Functional Modular Layout
When laying out the PCB, the entire circuit should first be divided into different modules according to function, such as power supply modules, MCU core modules, communication interface modules, sensor interface modules, etc.
Components within each module should be placed close together, while maintaining appropriate distance between modules. This facilitates routing and improves signal integrity.
For example, in my STM32 projects, the layout is typically as follows:
Power Supply Module: Placed on the edge or corner of the PCB, including power input interfaces, voltage regulator chips, and filter capacitors.
MCU Core Area: Placed in the center of the PCB, surrounded by crystal oscillators, reset circuits, decoupling capacitors, etc.
Peripheral Interfaces: Placed on the edge of the PCB according to actual interface location requirements, such as USB interfaces, serial ports, CAN interfaces, etc.
Analog Circuits: If there are analog circuits such as ADCs and DACs, they should be kept away from digital circuits and high-frequency signal sources to reduce interference.
Signal Flow Layout
When laying out the circuit, the signal flow should be considered, ensuring that signals flow from input to output as much as possible, avoiding signal backflow or crossing.
For example, in a data acquisition system, sensor signals should first pass through a signal conditioning circuit, then enter the ADC, and finally reach the MCU. This layout minimizes signal interference.
Thermal Management Considerations
For high-power components, such as power chips, power devices, and high-speed processors, heat dissipation must be considered during layout. These components should:
Be away from heat-sensitive components (such as crystal oscillators and sensors).
Be close to the PCB edge or heat dissipation holes.
Reserve sufficient copper foil for heat dissipation.
Reserve space for heat sink installation if necessary.
In automotive electronics projects, we often encounter high-temperature environments, making thermal management particularly important.
Once, in one of our vehicle controller designs, improper power chip layout led to excessively high local temperatures, ultimately requiring a PCB redesign with increased heat dissipation copper area.
Mechanical Structure Compatibility
The PCB's dimensions, mounting hole positions, and interface positions must match the product's mechanical structure.
Before layout, it's best to obtain the product's 3D structural drawing to ensure the PCB can be correctly installed in the housing and all interfaces align with housing openings.
